This invention relates to sprinkler devices and more specifically, to an improved sprinkler which incorporates a spray plate (or rotor plate) mounted for wobbling/rotating motion referred to herein as xe2x80x9cnutation.xe2x80x9d
Moving irrigation systems such as conventional pivot or linear systems are known to incorporate conduit truss span assemblies which mount sprinkler heads, spaced along the truss assemblies for sprinkling or irrigating relatively large areas of land. The sprinkling heads may be mounted on top of the truss assemblies in a normal upright position, or they may be inverted and suspended from the span assemblies by means of drop tubes. Sprinkler heads are typically of the spinner type, which incorporate rotatable stream distributors (also referred to as rotor plates or spray plates, fixed spray plates or bubbler devices).
When irrigating large areas of land with pivot or linear sprinklers, the sprinklers need to be spaced apart as far as possible to minimize system hardware costs. To obtain an even distribution of the water at wide spacings requires sprinklers that simultaneously throw the water long distances and produce sprinkling patterns that are very even when overlapped with adjacent sprinklers. These two requirements are somewhat exclusive in that maximum radius of throw is achieved with concentrated streams of water shooting at relatively high trajectory angles. These streams, however, tend to produce a donut shaped sprinkling pattern at low pressure that does not overlap evenly. The use of nutating or wobbling sprinklers to enhance distribution uniformity particularly at low pressure is known in the art, as evidenced, for example, by U.S. Pat. Nos. 5,439,174; 5,671,885; and 5,588,595. Wobbling type sprinklers can be problematic, however, in the sense that in some circumstances, the sprinkler simply rotates on its center axis without wobbling. This is particularly true if the sprinkler rotor plate is allowed to assume an on-center orientation when at rest.
A recently issued U.S. Pat. No. 5,950,927, addresses this problem by mechanically constraining the rotor plate to always assume an off-center position.
This invention provides an improved rotor plate mounting arrangement in a nutating sprinkler which insures that the rotor plate will be tilted to an off-center position on start-up, thereby also insuring that the rotor plate will exhibit the desired nutating motion.
In a first exemplary embodiment, the rotor plate is supported in a center body of a removable cap assembly secured to a sprinkler body, with the rotor plate downstream of a fixed nozzle. The rotor plate is fixed to a hub protruding from the center of one side of a load disc captured loosely between a pair of annular rings located within the centerbody. In this embodiment, the hub includes a shaft extending into the rotor plate. At the same time, a tilter button or post projects upwardly toward the opposite side of the load disc and engages a center portion of the disc when the sprinkler is at an at rest position. Because of the inherently unstable nature of the engagement, i.e., where a top heavy rotor plate is supported essentially on a point contact, the rotor plate will tilt to one side. When water is supplied to the sprinkler, the rotor plate will rotate and wobble, i.e., nutate, in the desired manner, and the rotor plate will also separate slightly from the tilter button or post, thus reducing the potential for wear on the post. In this first embodiment, the tilter button or post is incorporated in a plug which is threaded into a cap center body which supports the rotor plate. In another variation of this embodiment, the tilter button or post is incorporated in a cover or plate secured to the center body by one or more fasteners.
In a second exemplary embodiment of the invention, the hub includes a spool and a shaft projecting from one side of the spool, with the other end of the shaft fixed in the rotor plate. The spool has upper and lower flanges, and an internal annular ring in the cap centerbody loosely supports the spool in an area between the upper and lower flanges. A tilter button or post extends vertically into a center recess in the other side of the spool, creating an unstable mounting arrangement as described hereinabove. Here again, the rotor plate assumes a tilted or off-center position when at rest, insuring that the desired nutating motion will occur on start-up.
In a third embodiment of the invention, the rotor plate is formed with an open-ended cylindrical stem which receives a relatively large diameter hub projecting from the center of one side of a load disc. In this embodiment, the load disc is captured between a pair of discrete, annular rings sandwiched between an interior shoulder in the cap center body and the cap cover or plug. As in the earlier described embodiments, a tilter button or post is formed integrally with the cover or plug and engages a center recess in the other side of the load disc.
In a fourth embodiment of the invention, an open cylindrical stem of the rotor plate receives a hub projecting from one side of a spool loosely captured within the cap center body by an internal ring or flange. The upper and lower spool flanges may be snap-fitted together, sandwiching a wear resistant spool bushing therebetween. The internal ring is held in place in the center body by the cover or plug which includes an integral post or tilter button projecting into a center recess in the other side of the spool.
In a fifth and preferred embodiment of the invention, the open cylindrical stem of the rotor plate receives an upper spool component of a spool bearing assembly. This upper spool component is re-shaped to incorporate an umbrella-like shield over the spool or spindle bearing assembly to prevent dirt or debris from entering the bearing area. The lower spool or spindle component is made of brass and is shaped and sized to have sufficient mass to statically balance the moving parts about the center of nutation, while still producing the instability vis-a-vis the post that insures an off-center at rest position of the rotor plate.
Other advantages and improvements will be explained in further detail below.
Accordingly, in one aspect, the present invention relates to a nutating sprinkler assembly comprising a sprinkler body having one end adapted to be coupled to a water supply conduit and an opposite end supporting a nozzle; at least one arm extending from the sprinkler body for supporting a removable cap assembly downstream of the nozzle, the cap assembly having a center body supporting a rotor plate having off-center grooves for distributing a stream exiting the nozzle and impinging upon the grooves; a hub secured to the rotor body and comprising a spool bearing assembly having upper and lower bearing flanges; the center body mounting an interior ring loosely confining the spool bearing assembly between the upper and lower bearing flanges; the center body having an end wall formed with a post extending toward and received within a cavity of a post bearing component when the rotor plate is in an at-rest position, thereby creating an unstable arrangement causing the rotor plate to tilt to an off-center position, the spool bearing component comprised of a relatively heavy material for balancing the hub and the rotor body during nutation.